In detonating a plurality of blasting charges, transmission tubes may be deployed from a central initiating point to transmit initiation signals to detonate individual blasting charges. Although transmission tubes have been traditionally and primarily used for blasting initiation, there are a number of other uses for transmission tubes. For example, transmission tubes have been used to transmit an automobile collision impact signal to activate automatic inflation of an automobile protective air bag, or automatic pre-tensioning of automobile driver and passenger safety belts.
The aforementioned transmission tubes may be of the type disclosed in U.S. Pat. No. 3,590,739, sold under the trademark "Nonel", and sometimes referred to as "shock tube". As used herein, the term "transmission tube " refers to any detonating or deflagrating signal transmission tube or line including a flexible hollow tube, which can carry a detonating or deflagrating signal along its interior, which signal does not destroy the tube.
The term "signal" when used in connection with the aforementioned transmission tube is intended to refer to either the detonating shock wave or deflagrating flame front which is transmitted along the interior of the tube by combustion of a reactive substance contained therein.
In detonating a charge, or in activating an automobile safety feature, it is extremely important that the device used to transmit the signal to initiate these functions be reliable. However, in field use for blasting initiation, and also in heavy manufacturing environments, the reliability of transmission tubes may be inadvertently reduced. For example, if the environment seal of a transmission tube is breached, environmental contamination may be introduced into the transmission tube interior, thereby reducing the reliability of signal transmission.
It is therefore an object of the invention to provide a signal transmission device having improved reliability of signal transmission.
It is another object of the invention to provide a reliable signal transmission device having improved durability and impermeability to fluids.
It is a further object of the invention to provide a reliable signal transmission device, capable of transmitting a plurality of signals, that is easy to handle and deploy.
It is another object of the invention to provide an opaque signal transmission device which conceals a signal it is transmitting.
It is a further object of the invention to provide a reliable signal transmission device that is easy to manufacture and facile in its use.
It is another object of the invention to provide a reliable signal transmission device the continuity of which can be easily tested between the point of signal initiation and the destination point of the signal.
Other objects will be in part obvious and in part pointed out in more detail hereinafter.
A better understanding of the objects, advantages, features, properties and relations of the invention will be obtained from the following description and accompanying drawings which set forth certain illustrative embodiments and are indicative of the various ways in which the principles of the invention are employed.